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LMH0002: Output Level

user6308822
Prodigy 70 points
Part Number: LMH0002

Tool/software:

Hello, Team

We have a question about LMH0002SQ.
We use LMH0002SQE/NOPB for ASI driver.
In the specifications, the output (Vsdo) is written as 750 to 850mV (p-p) under the conditions (REF=750Ω1%).
When measured with the oscilloscope's maxhold setting, some ICs output more than 880mV.
This results exceed the specifications of the DVB-ASI standard.

We use this IC in a variety of products, all of which have the same circuit configuration.
Looking at some outputs, the results are low (819 (average), 832 (maxhold)) and high (869 (average), 884 (maxhold)).
There appears to be a difference in the output value depending on the LOT number. Also, there are some individuals with the same LOT number that are different.
The environment is the BNC connector at the DRIVER output circuit → BNC cable → 75Ω⇔50Ω converter → oscilloscope.
It says that the specified output (Vsdo) is 750 to 850mV (p-p) under the conditions (REF=750Ω1%), but does it vary as shown above?

Regarding the notation written in the data sheet, in terms of the oscilloscope, is it the result of max hold or the result of amplitude?
Under what conditions (measurement environment, circuit) are the results measured?

Best Regards,
Miyajima

  • 0
    TI__Expert 3480 points

    Hi Miyajima-san,

    Please allow me to check with my team and then I will get back to you shortly after.

    Best,

    Nick

  • 0 in reply to Nick Peabody
    TI__Expert 3480 points

    Hi Miyajima-san,

    The results in the datasheet are measured with a 1 meter BNC cable at the driver output of the LMH0002. The amplitude is then measured either with a video analyzer with a 75Ω input, or an oscilloscope with a 75Ω plug-in. In our measurement setup we do not use a 75Ω⇔50Ω converter. 

    Best,

    Nick

  • 0 in reply to Nick Peabody
    Prodigy 70 points

    Hello, Nick

    Thank you for your reply.


    In your measurement environment, what GHz band do you use an oscilloscope for measurements?

    I have attached our measured waveforms.
    We measured with a 2GHz band oscilloscope, and the results are the amplitude and p-p (maxhold).
    As a result, the waveform contains noise. The amplitude does not exceed the DVBASI standard of 880mv, but the p-p (maxhold) slightly exceeds it.
    Does the output of this device include noise like the attached waveform?
    We will now confirm whether the problem is caused by our circuit.

    There are differences in the output depending on the LOT number and individual (approximately 50mV as far as I've seen a few), but does this tend to be biased depending on the LOT?

    Best Regards,
    Miyajima

  • 0 in reply to user6308822
    TI__Guru**** 153401 points

    Hi Miyajima-san,

    Due to the US Labor Day holiday, the response to your question may be delayed. We will look into your question when we return tomorrow, Sept 3rd. Sorry for the wait and any inconvenience it may cause.

    Thanks,

    David